Malignancies Occurring during Therapy with Tyrosine Kinase Inhibitors (TKI) for Chronic Myeloid Leukemia (CML) and Other Hematologic Malignancies.

Background: Success of tyrosine kinase inhibitors (TKIs) (imatinib, dasatinib, nilotinib, bosutinib) in chronic myeloid leukemia (CML) has given patients (pts) hope for a long disease free survival, and with increased survival, may be some late effects of TKI treatment in the form of development of another malignancy. One prior report suggested an unexpected increased incidence of cancers among pts treated with imatinib after failure to interferon (Roy et al, Leukemia 2005).

Aims: To investigate the frequency and characteristics of 2^nd malignancies (other than AML, ALL or MDS) among pts with CML or other hematologic malignancies treated with TKI.

Methods: We analyzed the records of 1647 pts treated with TKIs at our institution: 384 in chronic phase treated with imatinib after interferon failure, 338 treated with imatinib in advanced phases, 312 treated with imatinib as initial therapy, 422 treated with 2^nd generation TKI after imatinib failure, and 109 treated with 2^nd generation TKI as frontline therapy.

Results: A total of 67 (4.07%) pts (47 male, 20 female) developed a 2^nd cancer. Their median age was 67 (range 31–85) years; the median follow-up after CML diagnosis was 94 (range 13–480) months (mo), and median time from start of TKI to development of another cancer was 38 (range 2–95) mo. These included 31/67(46%) pts who received imatinib as 1^st line therapy for median 39.5 (range 16–88) mo, 5 pts who received 2^nd generation TKI after imatinib failure (4 dasatinib, 1 bosutinib) for a median 10 (range 3–22) mo, and 1 pt received nilotinib as frontline therapy for 3 mo before diagnosis of 2^nd cancer. The accompanying table summarizes the findings. The most common cancer was non-melanoma skin cancer representing 31% of all cancers. Excluding these, the 2^nd cancers were seen in 2.8% of all pts treated. The skin cancers and melanomas were scattered and not localized to any particular anatomical site. Prostate cancer patients had median age 69 (range 43–83) years and imatinib treatment of median 38 (range 18–74) mo, for a cumulative incidence of 1.18% among male pts. Two patients with CLL were diagnosed on flow cytometry after loosing their hematologic response while still maintaining complete cytogenetic response (CCyR) on imatinib. After median follow up of 22 (range 1–95) mo from diagnosis of 2^nd cancer, 12 (18%) pts have died (none from 2^nd cancer). 49 pts continue on therapy with TKI after the diagnosis of 2^nd cancer with 15 in complete molecular response (CMR), 25 with complete cytogenetic response (CCyR), 4 with partial cytogenetic response (PCyR), 5 having only complete hematologic response (CHR). All the frontline imatinib patients who are alive with a second cancer are in CCyR except one who is having CHR only

BCC: basal cell carcinoma, SCC: squamous cell carcinoma, GU: genito-urinary, GI: gastro-intestinal, CLL: chronic lymphocytic leukemia, MPD: myeloproliferative disorder

Conclusion: Second cancers occur in a small percentage of pts receiving therapy with TKI for hematologic malignancies, mostly CML. These results need to be analyzed in the context of the underlying lifetime risk of developing cancer in the general population and in cancer survivors. There is no evidence at the moment to suggest that exposure to TKI is carcinogenic.